convert old "%-formatted" and .format(...) strings into "f-strings" with flynt

23 files changed, 108 insertions, 126 deletions

diff --git a/.github/workflows/pythonapp.yml b/.github/workflows/pythonapp.yml
index a244f20..620ca27 100644
--- a/.github/workflows/pythonapp.yml
+++ b/.github/workflows/pythonapp.yml
@@ -28,10 +28,10 @@ jobs:
         source $HOME/.poetry/env
         make tox-listenvs
 
-#    - name: Run linters
-#      run: |
-#        source $HOME/.poetry/env
-#        make lint
+    - name: Run linters
+      run: |
+        source $HOME/.poetry/env
+        make lint
 
     - name: Run tests with Python v3.8
       run: |
diff --git a/.travis.yml b/.travis.yml
index c2d158e..5ff3ee0 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -17,6 +17,7 @@ install:
 
 script:
   - make pytest
+  - make lint
 
 after_success:
   - coveralls
diff --git a/Makefile b/Makefile
index 669086e..866c16a 100644
--- a/Makefile
+++ b/Makefile
@@ -29,14 +29,15 @@ install: check-poetry ## install python-creole via poetry
 	poetry install
 
 lint: ## Run code formatters and linter
+	poetry run flynt --fail-on-change --line_length=119 creole
 # 	poetry run isort --check-only --recursive creole
 # 	poetry run black --line-length=119 --check creole
-	poetry run flake8 creole
+# 	poetry run flake8 creole
 
 fix-code-style: ## Fix code formatting
-# 	poetry run flynt --line_length=119 creole
+	poetry run flynt --line_length=119 creole
 # 	poetry run isort --apply --recursive creole
-	poetry run autopep8 --ignore-local-config --max-line-length=${MAX_LINE_LENGTH} --aggressive --aggressive --in-place --recursive creole
+# 	poetry run autopep8 --ignore-local-config --max-line-length=${MAX_LINE_LENGTH} --aggressive --aggressive --in-place --recursive creole
 
 tox-listenvs: check-poetry ## List all tox test environments
 	poetry run tox --listenvs
diff --git a/creole/cmdline.py b/creole/cmdline.py
index 78f4eb4..66e49be 100644
--- a/creole/cmdline.py
+++ b/creole/cmdline.py
@@ -1,11 +1,10 @@
-#!/usr/bin/env python
-# coding: utf-8
+#!/usr/bin/env python3
 
 """
     python-creole commandline interface
     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-    :copyleft: 2013 by the python-creole team, see AUTHORS for more details.
+    :copyleft: 2013-2020 by the python-creole team, see AUTHORS for more details.
     :license: GNU GPL v3 or above, see LICENSE for more details.
 """
 
@@ -27,8 +26,9 @@ class CreoleCLI(object):
                 " creole2html, html2creole, html2ReSt, html2textile"
             ),
         )
-        self.parser.add_argument('--version', action='version',
-            version='%%(prog)s from python-creole v%s' % VERSION_STRING
+        self.parser.add_argument(
+            '--version', action='version',
+            version='%%(prog)s from python-creole v%s' % VERSION_STRING # noqa flynt
         )
         self.parser.add_argument("sourcefile", help="source file to convert")
         self.parser.add_argument("destination", help="Output filename")
@@ -46,16 +46,14 @@ class CreoleCLI(object):
         self.convert(sourcefile, destination, encoding)
 
     def convert(self, sourcefile, destination, encoding):
-        print("Convert %r to %r with %s (codec: %s)" % (
-            sourcefile, destination, self.convert_func.__name__, encoding
-        ))
+        print(f"Convert {sourcefile!r} to {destination!r} with {self.convert_func.__name__} (codec: {encoding})")
 
         with codecs.open(sourcefile, "r", encoding=encoding) as infile:
             with codecs.open(destination, "w", encoding=encoding) as outfile:
                 content = infile.read()
                 converted = self.convert_func(content)
                 outfile.write(converted)
-        print("done. %r created." % destination)
+        print(f"done. {destination!r} created.")
 
 
 def cli_creole2html():
diff --git a/creole/emitter/creol2html_emitter.py b/creole/emitter/creol2html_emitter.py
index 76f6997..e583567 100644
--- a/creole/emitter/creol2html_emitter.py
+++ b/creole/emitter/creol2html_emitter.py
@@ -66,12 +66,12 @@ class TableOfContent(object):
         """Convert a python nested list like the one representing the toc to an html equivalent."""
         indent = "\t"*level
         if isinstance(nested_headlines, str):
-            return '%s<li><a href="#%s">%s</a></li>\n' % (indent, nested_headlines, nested_headlines)
+            return f'{indent}<li><a href="#{nested_headlines}">{nested_headlines}</a></li>\n'
         elif isinstance(nested_headlines, list):
-            html = '%s<ul>\n' % indent
+            html = f'{indent}<ul>\n'
             for elt in nested_headlines:
                 html += self.nested_headlines2html(elt, level + 1)
-            html += '%s</ul>' % indent
+            html += f'{indent}</ul>'
             if level > 0:
                 html += "\n"
             return html
@@ -239,15 +239,11 @@ class HtmlEmitter(object):
     #--------------------------------------------------------------------------
 
     def header_emit(self, node):
-        header = '<h%d>%s</h%d>' % (
-                node.level, self.html_escape(node.content), node.level
-        )
+        header = f'<h{node.level:d}>{self.html_escape(node.content)}</h{node.level:d}>'
         if self.toc is not None:
             self.toc.add_headline(node.level, node.content)
             # add link attribute for toc navigation
-            header = '<a name="%s">%s</a>' % (
-                self.html_escape(node.content), header
-            )
+            header = f'<a name="{self.html_escape(node.content)}">{header}</a>'
 
         header += "\n"
         return header
@@ -262,8 +258,7 @@ class HtmlEmitter(object):
         else:
             inside = self.html_escape(target)
 
-        return '<a href="%s">%s</a>' % (
-            self.attr_escape(target), inside)
+        return f'<a href="{self.attr_escape(target)}">{inside}</a>'
 
     def image_emit(self, node):
         target = node.content
@@ -281,8 +276,7 @@ class HtmlEmitter(object):
                         self.attr_escape(target), title, title, width, height)
             except:
                 pass
-        return '<img src="%s" title="%s" alt="%s" />' % (
-            self.attr_escape(target), text, text)
+        return f'<img src="{self.attr_escape(target)}" title="{text}" alt="{text}" />'
 
     def macro_emit(self, node):
         #print(node.debug())
@@ -296,9 +290,7 @@ class HtmlEmitter(object):
         except ValueError as e:
             exc_info = sys.exc_info()
             return self.error(
-                "Wrong macro arguments: %s for macro '%s' (maybe wrong macro tag syntax?)" % (
-                    json.dumps(args), macro_name
-                ),
+                f"Wrong macro arguments: {json.dumps(args)} for macro '{macro_name}' (maybe wrong macro tag syntax?)",
                 exc_info
             )
 
@@ -318,14 +310,14 @@ class HtmlEmitter(object):
 
         if macro == None:
             return self.error(
-                "Macro '%s' doesn't exist" % macro_name,
+                f"Macro '{macro_name}' doesn't exist",
                 exc_info
             )
 
         try:
             result = macro(**macro_kwargs)
         except TypeError as err:
-            msg = "Macro '%s' error: %s" % (macro_name, err)
+            msg = f"Macro '{macro_name}' error: {err}"
             exc_info = sys.exc_info()
             if self.verbose > 1:
                 if self.verbose > 2:
@@ -342,22 +334,22 @@ class HtmlEmitter(object):
                     try:
                         sourceline = inspect.getsourcelines(macro)[0][0].strip()
                     except IOError as err:
-                        evalue = etype("%s (error getting sourceline: %s from %s)" % (evalue, err, filename))
+                        evalue = etype(f"{evalue} (error getting sourceline: {err} from {filename})")
                     else:
-                        evalue = etype("%s (sourceline: %r from %s)" % (evalue, sourceline, filename))
+                        evalue = etype(f"{evalue} (sourceline: {sourceline!r} from {filename})")
                     exc_info = etype, evalue, etb
 
             return self.error(msg, exc_info)
         except Exception as err:
             return self.error(
-                "Macro '%s' error: %s" % (macro_name, err),
+                f"Macro '{macro_name}' error: {err}",
                 exc_info=sys.exc_info()
             )
 
         if not isinstance(result, str):
-            msg = "Macro '%s' doesn't return a unicode string!" % macro_name
+            msg = f"Macro '{macro_name}' doesn't return a unicode string!"
             if self.verbose > 1:
-                msg += " - returns: %r, type %r" % (result, type(result))
+                msg += f" - returns: {result!r}, type {type(result)!r}"
             return self.error(msg)
 
         if node.kind == "macro_block":
@@ -388,7 +380,7 @@ class HtmlEmitter(object):
 
     def default_emit(self, node):
         """Fallback function for emitting unknown nodes."""
-        raise NotImplementedError("Node '%s' unknown" % node.kind)
+        raise NotImplementedError(f"Node '{node.kind}' unknown")
 
     def emit_children(self, node):
         """Emit all the children of a node."""
@@ -397,7 +389,7 @@ class HtmlEmitter(object):
     def emit_node(self, node):
         """Emit a single node."""
         #print("%s_emit: %r" % (node.kind, node.content))
-        emit = getattr(self, '%s_emit' % node.kind, self.default_emit)
+        emit = getattr(self, f'{node.kind}_emit', self.default_emit)
         return emit(node)
 
     def emit(self):
@@ -418,7 +410,7 @@ class HtmlEmitter(object):
             self.stderr.write(exception)
 
         if self.verbose > 0:
-            return "[Error: %s]\n" % text
+            return f"[Error: {text}]\n"
         else:
             # No error output
             return ""
diff --git a/creole/emitter/html2creole_emitter.py b/creole/emitter/html2creole_emitter.py
index 00fd142..4a191b3 100644
--- a/creole/emitter/html2creole_emitter.py
+++ b/creole/emitter/html2creole_emitter.py
@@ -43,7 +43,7 @@ class CreoleEmitter(BaseEmitter):
         return "{{{%s}}}" % self.deentity.replace_all(node.content)
 
     def blockdata_pass_emit(self, node):
-        return "%s\n\n" % node.content
+        return f"{node.content}\n\n"
         return node.content
 
     #--------------------------------------------------------------------------
@@ -101,9 +101,9 @@ class CreoleEmitter(BaseEmitter):
             # e.g.: <a name="anchor-one">foo</a>
             return link_text
         if link_text == url:
-            return "[[%s]]" % url
+            return f"[[{url}]]"
         else:
-            return "[[%s|%s]]" % (url, link_text)
+            return f"[[{url}|{link_text}]]"
 
     def img_emit(self, node):
         src = node.attrs["src"]
diff --git a/creole/emitter/html2rest_emitter.py b/creole/emitter/html2rest_emitter.py
index 0e0b663..9c46313 100644
--- a/creole/emitter/html2rest_emitter.py
+++ b/creole/emitter/html2rest_emitter.py
@@ -61,14 +61,14 @@ class ReStructuredTextEmitter(BaseEmitter):
         """ pre block -> with newline at the end """
         pre_block = self.deentity.replace_all(node.content).strip()
         pre_block = "\n".join(["    %s" % line for line in pre_block.splitlines()])
-        return "::\n\n%s\n\n" % pre_block
+        return f"::\n\n{pre_block}\n\n"
 
     def inlinedata_pre_emit(self, node):
         """ a pre inline block -> no newline at the end """
         return "<pre>%s</pre>" % self.deentity.replace_all(node.content)
 
     def blockdata_pass_emit(self, node):
-        return "%s\n\n" % node.content
+        return f"{node.content}\n\n"
         return node.content
 
     #--------------------------------------------------------------------------
@@ -212,16 +212,16 @@ class ReStructuredTextEmitter(BaseEmitter):
             if not old_url:
                 # new substitution
                 self._substitution_data.append(
-                    ".. _%s: %s" % (link_text, url)
+                    f".. _{link_text}: {url}"
                 )
-            return "`%s`_" % link_text
+            return f"`{link_text}`_"
 
         if old_url:
             # reuse a existing substitution
-            return "`%s`_" % link_text
+            return f"`{link_text}`_"
         else:
             # create a inline hyperlink
-            return "`%s <%s>`_" % (link_text, url)
+            return f"`{link_text} <{url}>`_"
 
     def img_emit(self, node):
         src = node.attrs["src"]
@@ -244,10 +244,10 @@ class ReStructuredTextEmitter(BaseEmitter):
         )
         if not old_src:
             self._substitution_data.append(
-                ".. |%s| image:: %s" % (substitution_text, src)
+                f".. |{substitution_text}| image:: {src}"
             )
 
-        return "|%s|" % substitution_text
+        return f"|{substitution_text}|"
 
     #--------------------------------------------------------------------------
 
@@ -270,7 +270,7 @@ class ReStructuredTextEmitter(BaseEmitter):
         if node.level == 1:
             # FIXME: This should be made ​​easier and better
             complete_list = "\n\n".join([i.strip("\n") for i in content.split("\n") if i])
-            content = "%s\n\n" % complete_list
+            content = f"{complete_list}\n\n"
 
         return content
 
@@ -291,7 +291,7 @@ class ReStructuredTextEmitter(BaseEmitter):
         )
         self.emit_children(node)
         content = self._table.get_rest_table()
-        return "%s\n\n" % content
+        return f"{content}\n\n"
 
 
 if __name__ == '__main__':
diff --git a/creole/emitter/html2textile_emitter.py b/creole/emitter/html2textile_emitter.py
index e43b0df..0326ec9 100644
--- a/creole/emitter/html2textile_emitter.py
+++ b/creole/emitter/html2textile_emitter.py
@@ -43,7 +43,7 @@ class TextileEmitter(BaseEmitter):
         return "<pre>%s</pre>" % self.deentity.replace_all(node.content)
 
     def blockdata_pass_emit(self, node):
-        return "%s\n\n" % node.content
+        return f"{node.content}\n\n"
         return node.content
 
 
@@ -53,7 +53,7 @@ class TextileEmitter(BaseEmitter):
         return "%s\n\n" % self.emit_children(node)
 
     def headline_emit(self, node):
-        return "h%i. %s\n\n" % (node.level, self.emit_children(node))
+        return f"h{node.level:d}. {self.emit_children(node)}\n\n"
 
     #--------------------------------------------------------------------------
 
@@ -96,7 +96,7 @@ class TextileEmitter(BaseEmitter):
     def a_emit(self, node):
         link_text = self.emit_children(node)
         url = node.attrs["href"]
-        return '"%s":%s' % (link_text, url)
+        return f'"{link_text}":{url}'
 
     def img_emit(self, node):
         src = node.attrs["src"]
@@ -114,7 +114,7 @@ class TextileEmitter(BaseEmitter):
         if text == "": # Use filename as picture text
             text = posixpath.basename(src)
 
-        return "!%s(%s)!" % (src, text)
+        return f"!{src}({text})!"
 
     #--------------------------------------------------------------------------
 
diff --git a/creole/html_tools/deentity.py b/creole/html_tools/deentity.py
index fd23782..1f706ae 100644
--- a/creole/html_tools/deentity.py
+++ b/creole/html_tools/deentity.py
@@ -67,7 +67,7 @@ class Deentity(object):
             groups = match.groupdict()
             for name, text in groups.items():
                 if text is not None:
-                    replace_method = getattr(self, 'replace_%s' % name)
+                    replace_method = getattr(self, f'replace_{name}')
                     return replace_method(text)
 
             # Should never happen:
diff --git a/creole/parser/creol2html_parser.py b/creole/parser/creol2html_parser.py
index 7c519d8..9e97031 100644
--- a/creole/parser/creol2html_parser.py
+++ b/creole/parser/creol2html_parser.py
@@ -357,7 +357,7 @@ class CreoleParser(object):
         self.cur = DocNode(key, self.cur)
 
         self.text = None
-        text = groups["%s_text" % key]
+        text = groups[f"{key}_text"]
         self.parse_inline(text)
 
         self.cur = self._upto(self.cur, (key,)).parent
@@ -431,7 +431,7 @@ class CreoleParser(object):
                 if self.debug and name != "char":
                     # TODO: use logging
                     debug(groups)
-                replace_method = getattr(self, '_%s_repl' % name)
+                replace_method = getattr(self, f'_{name}_repl')
                 replace_method(groups)
                 return
 
@@ -465,7 +465,7 @@ class CreoleParser(object):
             start_node = self.root
             print("  document tree:")
         else:
-            print("  tree from %s:" % start_node)
+            print(f"  tree from {start_node}:")
 
         print("=" * 80)
         def emit(node, ident=0):
diff --git a/creole/parser/html_parser.py b/creole/parser/html_parser.py
index 6cd1c88..741754f 100644
--- a/creole/parser/html_parser.py
+++ b/creole/parser/html_parser.py
@@ -96,11 +96,11 @@ class HtmlParser(HTMLParser):
 
     def _pre_cut(self, data, type, placeholder):
         if self.debugging:
-            print("append blockdata: %r" % data)
+            print(f"append blockdata: {data!r}")
         assert isinstance(data, str), "blockdata is not unicode"
         self.blockdata.append(data)
         id = len(self.blockdata) - 1
-        return '<%s type="%s" id="%s" />' % (placeholder, type, id)
+        return f'<{placeholder} type="{type}" id="{id}" />'
 
     def _pre_pre_inline_cut(self, groups):
         return self._pre_cut(groups["pre_inline"], "pre", self._inline_placeholder)
@@ -120,7 +120,7 @@ class HtmlParser(HTMLParser):
             if text is not None:
                 if self.debugging:
                     print("%15s: %r (%r)" % (name, text, match.group(0)))
-                method = getattr(self, '_pre_%s_cut' % name)
+                method = getattr(self, f'_pre_{name}_cut')
                 return method(groups)
 
 #        data = match.group("data")
@@ -175,7 +175,7 @@ class HtmlParser(HTMLParser):
     #-------------------------------------------------------------------------
 
     def handle_starttag(self, tag, attrs):
-        self.debug_msg("starttag", "%r atts: %s" % (tag, attrs))
+        self.debug_msg("starttag", f"{tag!r} atts: {attrs}")
 
         if tag in IGNORE_TAGS:
             return
@@ -200,26 +200,26 @@ class HtmlParser(HTMLParser):
             self.cur = DocNode(tag, self.cur, None, attrs)
 
     def handle_data(self, data):
-        self.debug_msg("data", "%r" % data)
+        self.debug_msg("data", f"{data!r}")
         assert isinstance(data, str)
         DocNode("data", self.cur, content=data)
 
     def handle_charref(self, name):
-        self.debug_msg("charref", "%r" % name)
+        self.debug_msg("charref", f"{name!r}")
         DocNode("charref", self.cur, content=name)
 
     def handle_entityref(self, name):
-        self.debug_msg("entityref", "%r" % name)
+        self.debug_msg("entityref", f"{name!r}")
         DocNode("entityref", self.cur, content=name)
 
     def handle_startendtag(self, tag, attrs):
-        self.debug_msg("startendtag", "%r atts: %s" % (tag, attrs))
+        self.debug_msg("startendtag", f"{tag!r} atts: {attrs}")
         attr_dict = dict(attrs)
         if tag in (self._block_placeholder, self._inline_placeholder):
             id = int(attr_dict["id"])
 #            block_type = attr_dict["type"]
             DocNode(
-                "%s_%s" % (tag, attr_dict["type"]),
+                f"{tag}_{attr_dict['type']}",
                 self.cur,
                 content=self.blockdata[id],
 #                attrs = attr_dict
@@ -231,7 +231,7 @@ class HtmlParser(HTMLParser):
         if tag in IGNORE_TAGS:
             return
 
-        self.debug_msg("endtag", "%r" % tag)
+        self.debug_msg("endtag", f"{tag!r}")
 
         if tag == "br": # handled in starttag
             return
@@ -263,7 +263,7 @@ class HtmlParser(HTMLParser):
             start_node = self.root
             print("  document tree:")
         else:
-            print("  tree from %s:" % start_node)
+            print(f"  tree from {start_node}:")
 
         print("=" * 80)
         def emit(node, ident=0):
@@ -271,13 +271,13 @@ class HtmlParser(HTMLParser):
                 txt = "%s%s" % (" " * ident, child.kind)
 
                 if child.content:
-                    txt += ": %r" % child.content
+                    txt += f": {child.content!r}"
 
                 if child.attrs:
-                    txt += " - attrs: %r" % child.attrs
+                    txt += f" - attrs: {child.attrs!r}"
 
                 if child.level != None:
-                    txt += " - level: %r" % child.level
+                    txt += f" - level: {child.level!r}"
 
                 print(txt)
                 emit(child, ident + 4)
diff --git a/creole/rest_tools/clean_writer.py b/creole/rest_tools/clean_writer.py
index b6272ab..c56e44b 100644
--- a/creole/rest_tools/clean_writer.py
+++ b/creole/rest_tools/clean_writer.py
@@ -74,7 +74,7 @@ class CleanHTMLTranslator(html4css1.HTMLTranslator, object):
 
         if tagname in IGNORE_TAGS:
             if DEBUG:
-                print("ignore tag %r" % tagname)
+                print(f"ignore tag {tagname!r}")
             return ""
 
         parts = [tagname]
@@ -91,7 +91,7 @@ class CleanHTMLTranslator(html4css1.HTMLTranslator, object):
             if isinstance(value, list):
                 value = ' '.join([str(x) for x in value])
 
-            part = '%s="%s"' % (name.lower(), self.attval(str(value)))
+            part = f'{name.lower()}="{self.attval(str(value))}"'
             parts.append(part)
 
         if DEBUG:
@@ -105,7 +105,7 @@ class CleanHTMLTranslator(html4css1.HTMLTranslator, object):
             infix = ''
         html = '<%s%s>%s' % (' '.join(parts), infix, suffix)
         if DEBUG:
-            print("startag html: %r" % html)
+            print(f"startag html: {html!r}")
         return html
 
     def visit_section(self, node):
@@ -180,7 +180,7 @@ class CleanHTMLTranslator(html4css1.HTMLTranslator, object):
                 align = node.parent['align']
 
             if align:
-                self.body[-1] = self.body[-1].replace(' />', ' align="%s" />' % align)
+                self.body[-1] = self.body[-1].replace(' />', f' align="{align}" />')
 
 
 
@@ -199,7 +199,7 @@ def rest2html(content, enable_exit_status=None, **kwargs):
     ...
     SystemExit: 13
     """
-    assert isinstance(content, str), "rest2html content must be %s, but it's %s" % (str, type(content))
+    assert isinstance(content, str), f"rest2html content must be {str}, but it's {type(content)}"
 
     settings_overrides = {
         "input_encoding": "unicode",
diff --git a/creole/setup_utils.py b/creole/setup_utils.py
index 36e30e1..2eb28ab 100644
--- a/creole/setup_utils.py
+++ b/creole/setup_utils.py
@@ -105,9 +105,7 @@ def get_long_description(package_root, filename="README.creole", raise_errors=No
             raise
         # Don't raise the error e.g. in ./setup install process
         evalue = sys.exc_info()[1]
-        long_description_rest = "[Error: %s]\n%s" % (
-            evalue, long_description_origin
-        )
+        long_description_rest = f"[Error: {evalue}]\n{long_description_origin}"
     else:
         if raise_errors:
             # Test created ReSt code like PyPi does it.
@@ -115,11 +113,11 @@ def get_long_description(package_root, filename="README.creole", raise_errors=No
             try:
                 pypi_rest2html(long_description_rest)
             except SystemExit as e:
-                msg = "Error creole2rest self test failed: rest2html() exist with status code: %s\n" % e.args[0]
+                msg = f"Error creole2rest self test failed: rest2html() exist with status code: {e.args[0]}\n"
                 sys.stderr.write(msg)
                 sys.exit(msg)
             except Exception as e:
-                sys.exit("ReSt2html error: %s" % e)
+                sys.exit(f"ReSt2html error: {e}")
             else:
                 if "check" in sys.argv:
                     print("Generating creole to ReSt to html, ok.")
diff --git a/creole/shared/base_emitter.py b/creole/shared/base_emitter.py
index a29c224..8113de1 100644
--- a/creole/shared/base_emitter.py
+++ b/creole/shared/base_emitter.py
@@ -38,7 +38,7 @@ class BaseEmitter(object):
     #--------------------------------------------------------------------------
 
     def blockdata_pass_emit(self, node):
-        return "%s\n\n" % node.content
+        return f"{node.content}\n\n"
         return node.content
 
     #--------------------------------------------------------------------------
@@ -57,11 +57,11 @@ class BaseEmitter(object):
             return self.deentity.replace_named(entity)
         except KeyError as err:
             if self.debugging:
-                print("unknown html entity found: %r" % entity)
-            return "&%s" % entity # FIXME
+                print(f"unknown html entity found: {entity!r}")
+            return f"&{entity}" # FIXME
         except UnicodeDecodeError as err:
             raise UnicodeError(
-                "Error handling entity %r: %s" % (entity, err)
+                f"Error handling entity {entity!r}: {err}"
             )
 
     def charref_emit(self, node):
@@ -98,7 +98,7 @@ class BaseEmitter(object):
 
     def li_emit(self, node):
         content = self.emit_children(node)
-        return "\n%s %s" % (self._inner_list, content)
+        return f"\n{self._inner_list} {content}"
 
     def _list_emit(self, node, list_type):
         start_newline = False
@@ -133,7 +133,7 @@ class BaseEmitter(object):
         )
         self.emit_children(node)
         content = self._table.get_table_markup()
-        return "%s\n" % content
+        return f"{content}\n"
 
     def tr_emit(self, node):
         self._table.add_tr()
@@ -167,7 +167,7 @@ class BaseEmitter(object):
         content = self.emit_children(node)
         content = self._escape_linebreaks(content)
         if node.kind in BLOCK_TAGS:
-            content = "%s\n\n" % content
+            content = f"{content}\n\n"
         return content
 
     def div_emit(self, node):
@@ -201,17 +201,15 @@ class BaseEmitter(object):
         def unicode_error(method_name, method, node, content):
             node.debug()
             raise AssertionError(
-                "Method '%s' (%s) returns no unicode - returns: %s (%s)" % (
-                    method_name, method, repr(content), type(content)
-                )
+                f"Method '{method_name}' ({method}) returns no unicode - returns: {repr(content)} ({type(content)})"
             )
 
         if node.level:
-            self.debug_msg("emit_node", "%s (level: %i): %r" % (node.kind, node.level, node.content))
+            self.debug_msg("emit_node", f"{node.kind} (level: {node.level:d}): {node.content!r}")
         else:
-            self.debug_msg("emit_node", "%s: %r" % (node.kind, node.content))
+            self.debug_msg("emit_node", f"{node.kind}: {node.content!r}")
 
-        method_name = "%s_emit" % node.kind
+        method_name = f"{node.kind}_emit"
         emit_method = getattr(self, method_name, None)
 
         if emit_method:
diff --git a/creole/shared/document_tree.py b/creole/shared/document_tree.py
index e5b7bcf..6198c8a 100644
--- a/creole/shared/document_tree.py
+++ b/creole/shared/document_tree.py
@@ -32,9 +32,7 @@ class DocNode:
 
         self.attrs = dict(attrs)
         if content:
-            assert isinstance(content, str), "Given content %r is not unicode, it's type: %s" % (
-                content, type(content)
-            )
+            assert isinstance(content, str), f"Given content {content!r} is not unicode, it's type: {type(content)}"
 
         self.content = content
         self.level = level
@@ -57,7 +55,7 @@ class DocNode:
         return str(self.__repr__())
 
     def __repr__(self):
-        return "<DocNode %s: %r>" % (self.kind, self.content)
+        return f"<DocNode {self.kind}: {self.content!r}>"
 #        return "<DocNode %s (parent: %r): %r>" % (self.kind, self.parent, self.content)
 
     def debug(self):
@@ -77,7 +75,7 @@ class DocNode:
         """
         print("_" * 80)
         print("\tDocNode - debug:")
-        print("str(): %s" % self)
+        print(f"str(): {self}")
         print("attributes:")
         for i in dir(self):
             if i.startswith("_") or i == "debug":
diff --git a/creole/shared/markup_table.py b/creole/shared/markup_table.py
index ec59e66..3cddccc 100644
--- a/creole/shared/markup_table.py
+++ b/creole/shared/markup_table.py
@@ -46,7 +46,7 @@ class MarkupTable(object):
                     if self.head_prefix and cell.startswith(self.head_prefix):
                         cell += " " # Headline
                     else:
-                        cell = " %s " % cell # normal cell
+                        cell = f" {cell} " # normal cell
                 line_cells.append(cell)
             cells.append(line_cells)
 
diff --git a/creole/shared/unknown_tags.py b/creole/shared/unknown_tags.py
index fe231f0..cf4aa4a 100644
--- a/creole/shared/unknown_tags.py
+++ b/creole/shared/unknown_tags.py
@@ -30,10 +30,10 @@ def _mask_content(emitter, node, mask_tag):
     content = emitter.emit_children(node)
     if not content:
         # single tag
-        return "<<%(mask_tag)s>><%(tag)s%(attrs)s /><</%(mask_tag)s>>" % tag_data
+        return f"<<{tag_data['mask_tag']}>><{tag_data['tag']}{tag_data['attrs']} /><</{tag_data['mask_tag']}>>"
 
-    start_tag = "<<%(mask_tag)s>><%(tag)s%(attrs)s><</%(mask_tag)s>>" % tag_data
-    end_tag = "<<%(mask_tag)s>></%(tag)s><</%(mask_tag)s>>" % tag_data
+    start_tag = f"<<{tag_data['mask_tag']}>><{tag_data['tag']}{tag_data['attrs']}><</{tag_data['mask_tag']}>>"
+    end_tag = f"<<{tag_data['mask_tag']}>></{tag_data['tag']}><</{tag_data['mask_tag']}>>"
 
     return start_tag + content + end_tag
 
@@ -47,9 +47,7 @@ def raise_unknown_node(emitter, node):
     """
     content = emitter.emit_children(node)
     raise NotImplementedError(
-        "Node from type '%s' is not implemented! (child content: %r)" % (
-            node.kind, content
-        )
+        f"Node from type '{node.kind}' is not implemented! (child content: {content!r})"
     )
 
 
@@ -89,10 +87,10 @@ def escape_unknown_nodes(emitter, node):
     content = emitter.emit_children(node)
     if not content:
         # single tag
-        return escape("<%(tag)s%(attrs)s />" % tag_data)
+        return escape(f"<{tag_data['tag']}{tag_data['attrs']} />")
 
-    start_tag = escape("<%(tag)s%(attrs)s>" % tag_data)
-    end_tag = escape("</%(tag)s>" % tag_data)
+    start_tag = escape(f"<{tag_data['tag']}{tag_data['attrs']}>")
+    end_tag = escape(f"</{tag_data['tag']}>")
 
     return start_tag + content + end_tag
 
diff --git a/creole/shared/utils.py b/creole/shared/utils.py
index cb55299..f80a8ef 100644
--- a/creole/shared/utils.py
+++ b/creole/shared/utils.py
@@ -79,7 +79,7 @@ def dict2string(d):
     attr_list = []
     for key, value in sorted(d.items()):
         value_string = json.dumps(value)
-        attr_list.append("%s=%s" % (key, value_string))
+        attr_list.append(f"{key}={value_string}")
     return " ".join(attr_list)
 
 
diff --git a/creole/tests/test_cli.py b/creole/tests/test_cli.py
index 74fc7d7..be5f944 100644
--- a/creole/tests/test_cli.py
+++ b/creole/tests/test_cli.py
@@ -93,9 +93,7 @@ class CreoleCLITests(BaseCreoleTest, SubprocessMixin, CliTestMixins):
 
     def test_version(self):
         for cmd in CMDS:
-            version_info = "%s from python-creole v%s" % (
-                cmd, VERSION_STRING
-            )
+            version_info = f"{cmd} from python-creole v{VERSION_STRING}"
             self.assertSubprocess(
                 popen_args=[cmd, "--version"],
                 retcode=0,
@@ -125,7 +123,7 @@ class CreoleCLITestsDirect(BaseCreoleTest, CliTestMixins):
         destfilepath = dest_file.name
 
         sys.argv = [cli_str, sourcefilepath, destfilepath]
-        cli = getattr(cmdline, "cli_%s" % cli_str)
+        cli = getattr(cmdline, f"cli_{cli_str}")
         cli()
 
         dest_file.seek(0)
diff --git a/creole/tests/test_creole2html.py b/creole/tests/test_creole2html.py
index b6f9ed0..dfa1246 100644
--- a/creole/tests/test_creole2html.py
+++ b/creole/tests/test_creole2html.py
@@ -70,7 +70,7 @@ class TestCreole2html(BaseCreoleTest):
             tb_lines += error_msg.splitlines()
             tb_lines += [" -"*40]
             tb = "\n".join([" >>> %s" % l for l in tb_lines])
-            msg = "%r not found in:\n%s" % (part, tb)
+            msg = f"{part!r} not found in:\n{tb}"
             # TODO: use assertIn if python 2.6 will be not support anymore.
             if part not in error_msg:
                 raise self.failureException(msg)
diff --git a/creole/tests/test_macros.py b/creole/tests/test_macros.py
index 2a036be..5069a27 100644
--- a/creole/tests/test_macros.py
+++ b/creole/tests/test_macros.py
@@ -28,7 +28,7 @@ def unittest_macro1(**kwargs):
     '[test macro1 - kwargs: a=1,b=2]'
     """
     kwargs = ','.join(['%s=%s' % (k, json.dumps(v)) for k, v in sorted(kwargs.items())])
-    return "[test macro1 - kwargs: %s]" % kwargs
+    return f"[test macro1 - kwargs: {kwargs}]"
 
 
 def unittest_macro2(char, text):
diff --git a/creole/tests/test_setup_utils.py b/creole/tests/test_setup_utils.py
index 30a532e..b912f92 100644
--- a/creole/tests/test_setup_utils.py
+++ b/creole/tests/test_setup_utils.py
@@ -44,12 +44,12 @@ class SetupUtilsTests(BaseCreoleTest):
     def test_creole_package_path(self):
         self.assertTrue(
             os.path.isdir(CREOLE_PACKAGE_ROOT),
-            "CREOLE_PACKAGE_ROOT %r is not a existing direcotry!" % CREOLE_PACKAGE_ROOT
+            f"CREOLE_PACKAGE_ROOT {CREOLE_PACKAGE_ROOT!r} is not a existing direcotry!"
         )
         filepath = os.path.join(CREOLE_PACKAGE_ROOT, "README.creole")
         self.assertTrue(
             os.path.isfile(filepath),
-            "README file %r not found!" % filepath
+            f"README file {filepath!r} not found!"
         )
 
     def test_get_long_description_without_raise_errors(self):
diff --git a/creole/tests/utils/base_unittest.py b/creole/tests/utils/base_unittest.py
index 26b67fa..4feb3b9 100644
--- a/creole/tests/utils/base_unittest.py
+++ b/creole/tests/utils/base_unittest.py
@@ -36,7 +36,7 @@ try:
     from creole.rest_tools.clean_writer import rest2html
 except DocutilsImportError as err:
     REST_INSTALLED = False
-    warnings.warn("Can't run all ReSt unittests: %s" % err)
+    warnings.warn(f"Can't run all ReSt unittests: {err}")
 else:
     REST_INSTALLED = True
 
@@ -85,7 +85,7 @@ class BaseCreoleTest(MarkupTest):
 
         print()
         print("_" * 79)
-        print(" Debug Text: %s:" % msg)
+        print(f" Debug Text: {msg}:")
         print(text)
         print("-" * 79)